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Friday, 20 April 2012

ASP Special Characters

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ASP Special Characters

All the special characters that you see when programming ASP can be a little overwhelming at first. This lesson is aimed at providing a succinct look at the most common special characters that occur within ASP. This lesson will cover the following character/symbol combinations:
  • &
  • '
  • _
  • :
  • .
  • <%...%>
  • <%=...%>
That's pretty ugly and confusing to look at, so let's get right in to the details of each of the symbols and see what they mean.

String Concatenation: The Ampersand &

You can combine strings with the ampersand character. It acts as a glue between one or more strings to create one large string. See our Strings Lesson for a more detailed look at strings and string concatenation. Below is an example of the ampersand concatenating two strings.

ASP Code:

<%
Dim myString
myString = "One String"
myString = myString & " another string"
Response.Write(myString)
%>

Display:

One String another string

ASP Comments: The Apostrophe '

The apostrophe is used to prevent the ASP interpreter from executing the text that follows. In ASP there is only the single line comment. Check out our ASP Comments Lesson for more information on comments. Below is an example of the apostrophe.

ASP Code:

<%
'This is a comment.
%>

Spanning Multiple Lines: The Underscore _

Sometimes you can't fit all your ASP code on one line because your string is too long, you are tabbed over too far or you just want to break up the statement. With the use of the underscore you can tell the ASP interpreter that you line of code continues to the next line. This allows you to have a single ASP statement span multiple lines.
In the following example we have such a huge piece of code we need to span over three lines.

ASP Code:

<%
Response.Write("This is probably the longest "&_
"string to be typed out on this page and maybe "&_
"even this whole tutorial on ASP!!!")
%>

Display:

This is probably the longest string to be typed out on this page and maybe even this whole tutorial on ASP!!!

Squishing Onto a Line: The Colon :

Sometimes you want to reduce the human readability of your code because you're either mentally disturbed or insane. The colon will help you satiate your crazy desires by letting you put multiple lines of ASP code onto a single line. Below is an example of how to make your code very hard to read!

ASP Code:

<%
Dim x
Dim y
Dim z
x=3 : y=25 : z=x-y : y=x*z : z=x*x-z+y : y=5*3*z*2/x
%>

Calling Methods: The Period .

ASP allows for Object Oriented Programming and these objects have methods that can only be called by first stating the object, then placing a period and finally calling the method by its name. The form for using the period is:
  • myObject.MethodName()
If you would like to learn more about ASP objects see our ASP Object Lesson.

Declaring ASP Code: The Percentage %

ASP files are often made up of a combination of HTML, some other stuff and ASP. The tag that you use to stake out an area for your ASP code does not resemble normal HTML tags. Instead it is almost like just an opening tag that can be stretched very, very, very long. You must use this character sequence to insert ASP code into your ASP files.

ASP Code:

<html>
<body>
<%
'My ASP code goes here.
%>
</body>
</html>

Write Shortcut: The Percentage Equal %=

The percentage equal special character sequence is a modified version of the standard ASP code marker. This modification allows for quick access to the Response.Write() method that is used to write information to the web browser.
This shortcut can be used to quickly print numbers, strings, variables and anything else you might throw at it. Below is a few examples of using this shortcut.

ASP Code:

<%=2%> <br />
<%="Hello"%> <br />
<%=Date()%>

Display:

2
Hello
4/20/2012

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